Multilayer structure having at least one polycarbonate layer

ABSTRACT

A multilayer composition comprising at least one polycarbonate layer, at least one polyolefin layer, and at least one olefin vinyl alcohol layer, said layers being adhered together by means of tie layers containing a tie material selected from modified polyolefin graft copolymers and olefin vinyl ester copolymers.

RELATED APPLICATIONS

This application is a continuation of copending application Ser. No.688,196, filed Jan 2, 1985, now U.S. Pat. No. 4,608, 311.

BACKGROUND OF THE INVENTION

The use of multilayer compositions for containers such as bottles, jarsand the like, and as packaging materials for storing food, beverages,and other perishable items has been known for quite some time. Theconcept of a multilayer structure is that the positive properties of twoor more materials are combined with the structural integrity of eachmaterial being essentially uncompromised. Usually the advantageous andpositive properties of one material off-set or counter-balance theweaker properties of the second material. Thus, for example,polycarbonate resins exhibit advantageous properties of excellent impactstrength and heat resistance. However, polycarbonate resins generallyexhibit relatively high permiability rates to water vapor and gas, suchas oxygen and carbon dioxide, transport. On the other hand, there areknown and available other polymeric materials which exhibit relativelygood resistance to the transmission of water vapor. Still other knownpolymeric materials exhibit good resistance to the transport of gasessuch as oxygen and carbon dioxide. However these types of resinsgenerally exhibit relatively poor resistance to impact and heat.Therefore, a multilayered structure can be hypothesized utilizing apolycarbonate resin layer in combination with one or more layerscomprised of a polymeric material which is resistant to water vaporand/or gas transport. Such a structure should exhibit resistance toimpact and heat as well as resistance to water vapor and/or gastransport.

Although such a multilayered structure can be hypothesized on the basisof laminating a material possessing certain strong properties with amaterial exhibiting weaknesses in those same properties, certainpractical considerations inhibit implementation of this theory. Thematerials in the proposed laminar structure are in intimate contact attheir interface. This juncture or interface should provide asufficiently strong interaction with respect to the processingconditions which the multilayered structure undergoes so that a tight,firm and durable bond is maintained. Such conditions to which themultilayered structure can be exposed include heat, pressure, humidity,liquid chemicals, gasses and the like, or various combinations of theseconditions. The propensity of the various layers to maintain this tight,firm and durable bond is generally known as the "compatibility" of theselayers. When materials are incompatible the utility of the multilayerstructure is severely inhibited or useless.

Aromatic polycarbonate resins are particularly useful for multilayertechnology because of their high heat resistance, impact resistance, andclarity. However, polycarbonate resins are generally incompatible tovarying degrees with a number of other resins.

It is an object of the instant invention to provide a multilayeredstructure which exhibits good resistance to impact and heat, resistswater vapor transmission and gas transport, and in which the variouslayers or laminae maintain a tight, firm and durable bond.

SUMMARY OF THE INVENTION

The instant invention is directed to a multilayered structure comprisedof at least one polycarbonate layer or ply, at least one olefin vinylalcohol copolymer layer or ply, and at least one polyolefin layer orply. These layers or plies are bonded together by means of appropriaterelatively thin tie or adhesive layers.

DESCRIPTION OF THE INVENTION

In accordance with the instant invention there is provided a novelmultilayer structure or laminate comprising at least one polycarbonatelayer, at least one olefin vinyl alcohol copolymer layer, and at leastone polyolefin layer, said layers tied or adhered together with asuitable tie layer disposed between said layers. In a preferredembodiment the polycarbonate and polyolefin layers comprise the outerlayers and the olefin vinyl alcohol layer is an intermediate layerdisposed between said polycarbonate and polyolefin layers and adheredthereto by means of suitable tie layers.

Aromatic polycarbonates are known materials which may be readilyprepared by reacting a dihydric phenol with a carbonate precursor in aninterfacial polvmerization process or via transesterification. Thesehigh molecular weight thermoplastic polycarbonates are well known in theart and are disclosed, along with methods for their preparation, interalia, in U.S. Pat. Nos. 2,999,835, 3,028,365, 3,275,601, 3,334,154 and3,989,672, all of which are hereby incorporated herein by reference.Typical of some of the dihydric phenols which may be employed in thepreparation of the polycarbonates are 2,2-bis(4-hydroxyphenyl)propane(bisphenol-A), 1,1-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxyphenyl)pentane,2,2-bis(2-methyl-4-hydroxyphenyl)propane,2,2-bis(2,6-dimethyl-4-hydroxyphenyl)propane,2,2-bis(2,6-dibromo-4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)cyclohexane, 1,3-bis(4-hydroxyphenyl)propane,4,4'-thiodiphenol, bis(3,5-diisopropyl-4-hydroxyphenyl)sulfone,p,p'-dihydroxydiphenyl, and bis(4-hydroxyphenyl)ether. Other usefuldihydric phenols are disclosed in U.S. Pat. Nos. 2,999,835, 3,028,365,3,334,154, 3,035,021, 3,036,036, 3,036,037, 3,036,038 and 3,036,039.

It is, of course, possible to employ two or more different dihydricphenols or a copolymer of a dihydric phenol with a glycol or withhydroxy or acid terminated polyester, or with a dibasic acid in theevent a carbonate copolymer or interpolymer rather than a homopolymer isdesired for use in the preparation of the carbonate polymers of theinstant invention. Also employed in the practice of this invention maybe blends of any of the above materials to provide the aromaticcarbonate polymer.

The carbonate precursor may be either a carbonyl halide, a carbonateester or a bishaloformate. The carbonyl halides which can be employedherein are carbonyl bromide, carbonyl chloride, and mixtures thereof.Typical carbonate esters which may be employed herein are diphenylcarbonate, di-(halo phenyl)carbonates such as di(chlorophenyl)carbonate,di(bromophenyl)carbonate, di(trichlorophenyl)carbonate,di(tribromophenyl)carbonate, etc., di(alkylphenyl) carbonates such asdi(toyl)carbonate, etc., di(naphthyl) carbonate,di(chloronaphthyl)carbonate, phenyl tolyl carbonate, chlorophenylchloronaphthyl carbonate, etc., or mixtures thereof. The bishaloformatessuitable for use herein include the bishaloformates of dihydric phenolssuch as bischloroformate of hydroquinone, bischloroformate ofbisphenol-A, and the like; or bishaloformates of glycols such as thebischloroformate of ethylene glycol, neopentyl glycol, polyethyleneglycol, and the like. While other carbonate precursors will occur tothose skilled in the art, carbonyl chloride, also known as phosgene, isthe preferred carbonate precursor.

The aromatic polycarbonates useful in the practice of the instantinvention may be prepared by employing a molecular weight regulator, anacid acceptor and a catalyst. The molecular weight regulators which maybe employed include the monohydric phenols such as phenol itself,chroman-I, and paratertiarybutyl phenol.

A suitable acid acceptor may be either an organic or an inorganic acidacceptor. A suitable organic acceptor is a tertiary amine and includessuch amines as pyridine, triethylamine, dimethylaniline, tributylamine,and the like. The inorganic acid acceptor may be one which can be ahydroxide, a carbonate, or phosphate of an alkali or alkaline earthmetal.

The catalysts which are employed in the preparation of the carbonatepolymers can be any of the suitable catalysts which aid thepolymerization reaction of the dihydric phenols with the carbonateprecursors. Suitable catalysts include, but are not limited to tertiaryamines such as triethyl amine, tripropyl amine, N,N-dimethylaniline,quaternary ammonium compounds and quaternary phosphonium compounds.

Particularly useful polycarbonates are those containing recurringstructural units represented by the general formula ##STR1## wherein: Ris independently selected from halogen and monovalent hydrocarbonradicals,

A is selected from divalent hydrocarbon radicals, ##STR2## b is eitherzero or one; and n is independently selected from positive integershaving a value of from 0 to 4 inclusive.

The monovalent hydrocarbon radicals represented by R include alkyl,cycloalkyl, aryl, aralkyl and alkaryl radicals. The divalent hydrocarbonradicals represented by A include alkylene, cycloalkylene, alkylideneand cycloalkylidene radicals.

Also included herein are the branched polycarbonates which are obtainedby the reaction of a dihydric phenol, a carbonate precursor, and apolyfunctional aromatic compound to provide a thermoplastic randomlybranched carbonate polymer. These polyfunctional aromatic compounds arewell known in the art and contain at least three functional groups whichmay be hydroxyl, carboxyl, carboxylic anhydride, haloformyl, or mixturesthereof. Some illustrative non-limiting examples of these polyfunctionalaromatic compounds include trimellitic anhydride, trimellitic acid,trimellityl trichloride, 4-chloroformyl phthalic anhydride, pyromelliticacid, pyromellitic dianhydride, mellitic acid, mellitic anhydride,trimesic acid, benzophenonetetracarboxylic acid,benzophenonetetracarboxylic anhydride, and the like.

Also included herein are blends of linear and branched polycarbonates.

Within the definition of aromatic polycarbonates are alsocopolyester-carbonates, that is the polymer derived from a dihydricphenol, a carbonate precursor, and an ester precursor such as adifunctional carboxylic acid or an acid halide. Thesecopolyester-carbonates are disclosed in U.S. Pat. No. 3,169,121, whichis hereby incorporated herein by reference.

The polyolefins, which comprise the second layer in the multilayerstructure of the instant invention, are well known in the art and aregenerally commercially available. Typical of the polyolefins arepolyethylene, polypropylene, polybutylene, polyisobutylene or any of thepolyolefins derived from olefin monomers having from two to about 8carbon atoms. Copolymers of the above may be employed and are includedwithin the term polyolefin. Examples of copolymers include copolymers ofethylene and propylene or ethylene and butene. The term copolymersincludes the usual copolymers, that is, random, random block, and blockcopolymers. Various densities of polyolefins can be employed in thisinvention and include high density polyethylene, linear low densitypolyethylene and low density polyethylene. The preferred polyolefin ispolypropylene.

The olefin vinyl alcohol copolymers which comprise the third layer ofthe multilayer structure of the instant invention are known in the artand are disclosed, inter alia, in U.S. Pat. No. 3,585,177, which ishereby incorporated herein by reference. These olefin vinyl alcoholcopolymers may be prepared by hydrolyzing olefin vinyl esters. Theolefins used in the preparation of the olefin vinyl alcohols are thelower alpha olefins of from 2 to 4 carbon atoms, e.g., ethylene,propylene, butene-1 and isobutylene. Especially preferred is ethylene.

Suitable vinyl esters which can be copolymerized with the olefinmonomers and subsequently hydrolyzed to form the olefin vinyl alcoholcopolymers include vinyl ester monomers of the general formula: ##STR3##wherein R¹ is selected from hydrogen, alkyl radicals of from 1 to about10 carbon atoms, and aryl radicals of from 6 to 12 carbon atoms. Someillustrative non-limiting examples of these vinyl esters include vinylformate, vinyl acetate, vinyl propionate, vinyl butyrate, and vinylbenzoate.

The preferred olefin vinyl alcohol copolymers are ethylene vinyl alcoholcopolymers wherein the ethylene content is from 5 to 40 weight percentbased on the weight of the copolymer. Especially preferred are ethylenevinly alcohol copolymers wherein the ethylene content is from 8.9 to36.7 weight percent. Most especially preferred are ethylene vinylalcohol copolymers wherein the ethylene content is from 12 to 29.8weight percent.

The residual ester content of the copolymer should be less than 3% andpreferably less than 2% by weight. Most preferably the ester content isless than 1% by weight. The preferred olefin vinyl alcohol copolymerscontain less than 2% homopolymers, and preferably less than 1%homopolymers.

The term olefin vinyl alcohol copolymers also includes those copolymerscontaining a synthetic or natural rubber component such as butadiene,isoprene, natural rubbers, acrylonitrile-butadiene-styrene terpolymers,ethylene-propylene copolymers and terpolymers, chlorinated rubbers, andthe like.

The tie layers joining the polycarbonate, olefin vinyl alcohol andpolyolefin layers together may consist of any of the known adhesivematerials which serve to bind or adhere these materials together andwhich are compatible with these materials. However, among thesematerials two types of materials are particularly preferred for use inthe tie layers of the instant invention. The first type of thesematerials are the olefin vinyl ester copolymers. These olefin vinylester copolymers are well known in the art and are generallycommercially available. These esters are prepared by thecopolymerization of an olefin and a vinyl ester. The olefins used in thepreparation of the olefin vinyl esters are the lower alpha olefins offrom 2 to 4 carbon atoms. An especially preferred olefin is ethylene.

The vinyl esters which can be copolymerized with the olefins are thevinyl ester monomers of Formula II. A particularly useful vinyl ester isvinyl acetate.

The preferred tie layers of this type are those comprised of ethylenevinyl acetate copolymers. Especially preferred ethylene vinyl acetatecopolymers are those wherein the acetate content is from about 15 toabout 35 percent based on the weight of the copolymer.

The second type of material which functions as an effective tie layer inthe instant invention is a modified polyolefin containing 0.01-10 weightpercent of an unsaturated carboxylic acid or anhydride component. Thepolyolefins used in the tie layer include homopolymers of alpha-olefinssuch as ethylene and propylene and copolymers of ethylene and otheralpha olefins such as ethylene-propylene copolymers, ethylene-butene-1copolymers, ethylene-hexane-1 copolymers and copolymers of alpha-olefinssuch as propylene-butene-1 copolymers.

These homopolymers and copolymers can be used as a blended mixture. Theunsaturated carboxylic acids and anhydrides thereof include acrylicacid, methacrylic acid, maleic acid, fumaric acid, itaconic acid,3,6-endomethylene tetrahydro phthalic acid and anhydrides thereof. It isespecially preferable to use acrylic acid acid or maleic anhydride. Themodified polyolefins can be produced by graft-polymerizing saidunsaturated carboxylic acid or anhydride to a polyolefin.

The graft-polymerization can be carried out by a method of melt blendinga polyolefin and said unsaturated carboxylic acid or anhydride with acatalyst in an extruder; or a method of mixing said unsaturatedcarboxylic acid or anhydride and a catalyst with a suspension ofpolyolefin in a medium and heating the mixture with stirring.

The modified polyolefin should contain an unsaturated carboxylic acidcomponent in an amount of 0.01 to 10 weight percent so as to givedesirable adhesive strength.

These modified polyolefins may be blended with 40-3 weight percent of arubber component having a Mooney viscosity 50 ML₁₊₄ (100° C.) of 40-150preferably 40-100 in accordance with ASTM D15. The typical rubbercomponents include natural rubber and synthetic rubbers such asstyrene-butadiene rubber, acrylonitrile-butadiene rubber, acryl rubber,urethane rubber, butyl rubber, chloroprene rubber, silicone rubber,polybutadiene rubber, ethylene-propylene rubber, and the like. Thepreferred rubbers are the ethylene-propylene rubber andethylene-propylene terpolymer having a third component ofethylidenenor-bornene.

These modified polyolefins are described in more detail in U.S. Pat. No.4,058,647, which is hereby incorporated herein by reference.

The multilayer structures can be readily prepared by standardtechniques, including co-extrusion through a feedblock or combination inthe die. The thickness of the layers may vary substantially and areobviously somewhat dependant upon the final use to which the multilayerstructure will be applied. Generally the polycarbonate, olefin vinylalcohol, and polyolefin layers have a thickness of from about 0.10 milto about 80 mils each. These layers preferably have a thickness of fromabout 0.25 to about 60 mils each, and more preferably from about 0.5 milto about 30 mils. The tie layers are usually significantly thinner thanthe polycarbonate, olefin vinyl alcohol, and polyolefin layers. Thethickness of the tie layers is a thickness which is effective to adhereor bond the polycarbonate, olefin vinyl alcohol, and polyolefin layerstogether. Generally this thickness is less than about 1 mil, althoughtie layers up to about 5 mils thick can be employed.

The multilayer structures of the instant invention contain at least onepolycarbonate layer, at least one olefin vinyl alcohol layer, and atleast one polyolefin layer. These layers are adhered together by meansof a thin tie layer of the aforedescribed adhesive materials interposedbetween each of these layers. In the instant multilayer structure thepolycarbonate, olefin vinyl alcohol, and polyolefin layers need not bearranged in any particular manner. Thus, for example, in a three layerstructure containing one polycarbonate layer, one olefin vinyl alcohollayer, and one polyolefin layer bonded together by a tie layerinterposed intermediate each of these layers the polycarbonate layer maybe adjacent to and bonded to either the olefin vinyl alcohol layer orthe polyolefin layer; the olefin vinyl alcohol layer may be adjacent toand bonded to either the polycarbonate layer or the polyolefin layer; orthe polyolefin layer may be adjacent to and bonded to either thepolycarbonate or the olefin vinyl alcohol layer. That is to say, in athree layer structure the polycarbonate and the polyolefin layers may bethe outer layers and the olefin vinyl alcohol layer may be the innerlayer disposed intermediate said polycarbonate and polyolefin outerlayers; the polycarbonate and the olefin vinyl alcohol layers may be theouter layers and the polyolefin layer may be the inner layer disposedintermediate said polycarbonate and olefin vinyl alcohol outer layers;or the olefin vinyl alcohol and polyolefin layers may be the outerlayers and the polycarbonate layer may be the inner layer disposedintermediate said polyolefin and olefin vinyl alcohol outer layers.

In the multilayer structures of the instant invention the tie layers maybe the same or they may be different. Thus, for example, in a threelayer structure containing two tie layers both of these tie layers maybe the same or one tie layer may be comprised of one of the preferredaforedescribed materials while the second tie layer is comprised of adifferent material.

The multilayer structure may comprise a simple laminate useful, forexample, as a tray or can be thermoformed or blow-molded into a varietyof structures including containers of various types.

A particularly useful multilayer structure of the instant invention is athree layer structure comprised of a polycarbonate outer layer, apolyolefin outer layer, and an olefin vinyl alcohol inner layer disposedintermediate said polycarbonate and polyolefin outer layers and bondedthereto by tie layers disposed intermediate said inner layer and saidtwo outer layers.

In preparing the laminates or containers of the instant invention therecan be significant wastage of the multilayer material. An example ofsuch material is the scrap material prepared when the pinch-off is madein co-extrusion blow molding. A further example of such material iscontainers of the multilayer material which have outlived theirusefulness. These multilayer scrap materials are reground thus formingblends of their components. The polycarbonate, polyolefin, and olefinvinyl alcohol layers are a major portion of the blends while the tielayers are a minor portion of the blends. Generally, the polycarbonate,polyolefin, and olefin vinyl alcohol constitute above about 70 weightpercent of the blends, preferably above about 85 weight percent of theblends. The tie materials constitute below about 30 weight percent ofthe blends, preferably below about 15 weight percent of the blends.Weight percent of the blends, as regards the tie material and thepolycarbonate, polyolefin, and olefin vinyl alcohol is determined basedon the total amounts of the tie material and the polycarbonate,polyolefin, and olefin vinyl alcohol present in the blends.

Generally, the instant blends contain:

(i) from about 5 to about 96 weight percent polycarbonate;

(ii) from about 1 to about 60 weight percent olefin vinyl alcohol;

(iii) from about 2 to about 85 weight percent polyolefin; and

(iv) from about 0.5 to about 25 weight percent of at least one tiematerial selected from the olefin vinyl esters and the modifiedpolyolefins described hereinafore.

Preferred blends comprise:

(i) from about 10 to about 85 weight percent polycarbonate;

(ii) from about 1 to about 30 weight percent olefin vinyl alcohol;

(iii) from about 5 to about 80 weight percent polyolefin; and

(iv) from about 1 to about 20 weight percent of at least one tiematerial selected from olefin vinyl esters and modified polyolefins.

The compositions of the instant invention may optionally contain organicor inorganic inert fillers. The fillers which may be used are preferablyparticulate fillers such as particulate glass, e.g., chopped glassfiber, glass rovings, glass microbaloons or microspheres, andpulverulent glass, clay, talc, mica, inorganic natural fibers, syntheticorganic fibers, alumina, graphite, silica, calcium carbonate, carbonblack, magnesia, and the like. Generally such fillers are added toreinforce the structural integrity of the composition, e.g., to inhibitsagging and/or improve the tensile strength and stiffness of thecomposition and also to reduce shrinkage, minimize crazing, and lowermaterial costs. Generally the amount of filler employed in thecompositions of the instant invention is in the range of from about 2 toabout 60 weight percent, preferably from about 5 to about 50 weightpercent, and especially from about 8 to about 30 weight percent based onthe combined weight of the components (i)-(iv) and the filler.

The compositions of the instant invention may also optionally contain animpact modifier to improve the impact properties of the compositions.Generally these impact modifiers are quite well known in the art andserve to upgrade the impact properties of polymers such aspolycarbonates. Examples of these impact modifiers include, but are notlimited to, the following general categories:

polyacrylates;

polyolefins;

rubbery dienic polymers; and

styrenic polymers.

The polyacrylates which may be employed as impact modifiers are rubberyhomopolymers or copolymers. In general the polyalkyl acrylates describedin Brinkman et al., U.S. Pat. No. 3,591,659, incorporated herein byreference, can be used, especially those containing units derived fromalkyl acrylates, particularly n-butyl acrylate. Acrylate containingcopolymers wherein the other monomer is, for example, derived from amethacrylate are also readily employable, see for example JapanesePatent Application Announcement No. 1968-18611, incorporated herein byreference. Preferably the acrylate resin will be in the form of arubber-elastic graft copolymer having a glass transition temperaturebelow about -20° C., preferably below about -40° C. Schlichting, U.S.Pat. No. 4,022,748, incorporated herein by reference. More preferably,the acrylate resin will comprise a multiple stage polymer having arubbery first stage (core) and a thermoplastic hard final stage (shell),see Farnham U.S. Pat. No 4,096,202, incorporated herein by reference.

The most preferred acrylate resin is a multi-phase compositeinterpolymer comprised of a C₁ -C₅ acrylate and a C₁ -C₅ methacrylate.These interpolymers consist of about 25 to 95 weight percent of a firstelastomeric phase polymerized from a monomer system comprising about 75to 99.8 weight percent of a C₁ -C₅ alkyl acrylate, 0.1 to 5 weightpercent of cross linking monomer, 0.1 to 5 weight percent by weight ofgraftlinking monomer, and about 75 to 5 weight percent of a final rigidthermoplastic phase polymerized in the presence of said elastomericphase.

The crosslinking monomer is a polyethylenically unsaturated monomerhaving a plurality of addition polymerizable reactive groups all ofwhich polymerize at substantially the same rate of reaction. Suitablecrosslinking monomers include polyacrylic and polymethacrylic esters ofpolyols such as butylene diacrylate and dimethacrylate, trimethylolpropane trimethacrylate, and the like; di and trivinyl benzene, vinylacrylate and methacrylate, and the like. The preferred crosslinkingmonomer is butylene diacrylate.

The graftlinking monomer is a polyethylenically unsaturated monomerhaving a plurality of addition polymerizable reactive groups, at leastone of which polymerizes at substantially different rates ofpolymerization from at least one other of said reactive groups. Thefunction of the graftlinking monomer is to provide a residual level ofunsaturation in the elastomeric phase, particularly in the latter stagesof polymerization and, consequently, at or near the surface of theelastomer particles.

When the rigid thermoplastic phase is subsequently polymerized at thesurface of the elastomer, the residual unsaturated additionpolymerizable reactive group contributed by the graftlinking monomerparticipates in the subsequent reaction so that at least a portion ofthe rigid phase is chemically attached to the surface of the elastomer.Among the effective graftlinking monomers are alkyl group containingmonomers of alkyl esters of ethylenically unsaturated acids such asallyl acrylate, allyl methacrylate, diallyl maleate, diallyl fumarate,and allyl acid itaconate. Somewhat less preferred are the diallyl estersof polycarboxylic acids which do not contain polymerizable unsaturation.The preferred graftlinking monomers are allyl methacrylate and diallylmaleate.

A most preferred interpolymer has only two stages, a first stagecomprising about 60 to 95 percent by weight of the interpolymer andbeing polymerized from a monomer system comprising 95 to 99.8 percent byweight butyl acrylate, 0.1 to 2.5 percent by weight butylene diacrylateas crosslinking agent, 0.1 to 2.5 percent by weight allyl methacrylateor diallyl maleate as a graft-linking agent, with a final stagepolymerized from about 60 to 100 percent by weight methyl methacrylate.The multiphase composite interpolymer Acryloid KM-330 available fromRohm and Haas is preferred. This interpolymer is comprised of smallquantities of crosslinking and graft monomers, about 80 weight percentn-butyl acrylate and about 20 weight percent methyl methacrylate.

The polyolefins which can be employed as impact modifiers arehomopolymers or copolymers. Examples of homopolymers includepolyethylene, polypropylene, polybutene-1, polyhexene and the like. Thepolymers include the standard high density polymers, low densitypolymers as well as the new linear low density polyolefins such as thelinear low density polyethylene made with butene-1 or octene-1. Otherexamples of copolymers containing at least one olefin monomer can beemployed. For example, copolymers of ethylene and propylene can beemployed as the impact modifier as well as a copolymer of an olefin andan acrylate such as ethylene ethyl acrylate, a copolymer available fromUnion Carbide as DPD-6169. Other higher olefin monomers can be employedas copolymers with alkyl acrylates, for example propylene and n-butylacrylate and the like. These polyolefin polymers can also be reactedwith rubbery dienes so as to form terpolymers of the EPDM family such asethylene propylene diene terpolymers, for example Epsyn 704 availablefrom Copolymer Rubbber.

Various rubbery polymers can also be employed as impact modifiers.Examples of such rubbery polymers include polybutadiene, polyisoprene,styrene-butadiene and various other copolymers having a rubbery dieneccomonomer.

Styrene containing polymers also can be employed as impact modifiers.Examples of such polymers include acrylonitrile-butadiene-styrene,styrene acrylonitrile, acrylonitrile-butadiene-alpha-methylstyrene,methacrylate-butadiene-styrene and other high impact styrene containingpolymers.

Other known impact modifiers include various elastomeric materials suchas organic silicone rubbers, organic silicone polysiloxane polymers,polysiloxane-polycarbonate block copolymers, elastomericfluorohydrocarbons, elastomeric polyesters, and the like.

Generally any minimum quantity of impact modifier which positivelyupgrades the impact strength of the compositions of the instantinvention can be employed. Greater than this minimize quantity may beemployed so long as the properties desired for a particular applicationof these compositions are substantially maintained. Generally a minimumof about two weight percent is sufficient to observe an increase in theimpact strength. A minimum of about four weight percent is preferred. Alevel of about 30 weight percent should generally not be exceeded,preferably about 20 weight percent. Weight percent is measured as theamount of impact modifier in the total of impact modifier plus thecomponents (i)-(iv) of the instant compositions.

The instant compositions can be injection molded into various parts andutilized wherein an aromatic polycarbonate can be employed. A moldedarticle with greater environmental stress resistance as well as easierprocessability is formed.

Generally the amounts of components (i)-(iv) will depend upon thethicknesses and number of the various layers, including the tie layers,present in the multilayer structure from which the instant blends areformed. Component (iv) depends upon whether only one tie material ispresent in the multilayer structure or two different tie materials areutilized, i.e., two different tie layers are present. Component (iv) ispresent in minor amounts while components (i)-(iii), in combination, arepresent in major amounts in the instant blends.

The multilayered structures of the instant invention exhibit thetoughness and impact resistance of polycarbonate structures, and alsoexhibit improved resistance to water vapor and gas transport. They are,therefore, quite useful as packaging for foodstuffs, medicines, andother perishable items.

DESCRIPTION OF THE PPEFERRED EMBODIMENT

In order to more fully and clearly illustrate the present invention thefollowing examples are set forth. It is intended that the examples beconsidered as illustrative rather than limiting the invention asdisclosed and claimed herein. In the examples all parts and percents areon a weight basis unless otherwise indicated.

The following examples illustrate the blends of the instant invention.

EXAMPLE 1

A mixture of pellets comprised of 10 weight percent polycarbonate¹pellets, 74 weight percent polypropylene² pellets, 9 weight percentethylene vinyl alcohol³ pellets, and 7 weight percent of ethylene vinylacetate⁴ pellets is prepared by blending the pellets together andphysically mixing them for 5 minutes. This mixture is then fed to anextruder operating at a temperature of 450°-500° F. The extruded strandsare chopped into pellets and the pellets are injection molded at460°-480° F. into standard test bars.

These test bars are subjected to a variety of tests to determine theirphysical properties. These tests include ASTM D648, Heat DistortionTemperature Under Load (DTUL); Flexural Strength and Flexural Modulus,ASTM D790; Notched Izod Impact Strength (NI), ASTM D256; and GardnerImpact Strength. The results of these tests are set forth in Table I.

EXAMPLE 2

The procedure of Example 1 is substantially repeated except the mixturecontains 22 weight percent polycarbonate, 65 weight percentpolypropylene, 9 weight percent ethylene vinyl alcohol, and 4 weightpercent ethylene vinyl acetate.

EXAMPLE 3

The procedure of Example 1 is substantially repeated except that themixture contains 63 weight percent polycarbonate, 20 weight percentpolypropylene, 10 weight percent ethylene vinyl alcohol, and 7 weightpercent ethylene vinyl acetate.

The following examples illustrate the blends of the instant inventionwhich additionally contain an impact modifier.

EXAMPLE 4

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 10 parts per hundred parts of resin of anEPDM type impact modifier marketed by the Good Year Company under thedesignation EPDM 847G-9.

EXAMPLE 5

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 20 parts per hundred parts of resin ofEPDM 847G-9.

EXAMPLE 6

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 30 parts per hundred parts of resin ofEPDM 847G-9.

EXAMPLE 7

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 5 parts per hundred parts of resin ofethylene ethyl acrylate

EXAMPLE 8

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 10 parts per hundred parts of resin ofethylene ethyl acrylate

EXAMPLE 9

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 15 parts per hundred parts of resin ofethylene ethyl acrylate.

The following examples illustrate the blends of the instant inventionwhich additionally contain a filler.

EXAMPLE 10

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 10 parts per hundred parts of resin oftalc.

EXAMPLE 11

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 20 parts per hundred parts of resin oftalc.

EXAMPLE 12

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 30 parts per hundred parts of resin oftalc.

EXAMPLE 13

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 40 parts per hundred parts of resin oftalc.

EXAMPLE 14

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 10 parts per hundred parts of resin ofCaCO₃.

EXAMPLE 15

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 20 parts per hundred parts of resin ofCaC₃.

EXAMPLE 16

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 30 parts per hundred parts of resin ofCaCO₃.

EXAMPLE 17

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 40 parts per hundred parts of resin ofCaCO₃.

EXAMPLE 18

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 15 parts per hundred parts of resin ofmica.

EXAMPLE 19

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 30 parts per hundred parts of resin ofmica.

EXAMPLE 20

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 45 parts per hundred parts of resin ofmica.

EXAMPLE 21

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 10 parts per hundred parts of resin of3/16" long fiberglass.

EXAMPLE 22

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 20 parts per hundred parts of resin of3/16" long fiberglass.

EXAMPLE 23

The procedure of Example 1 is substantially repeated except that theresin mixture is admixed with 30 parts per hundred parts of resin of3/16" long fiberglass.

EXAMPLE 24

The procedure of Example 21 is substantially repeated except that thefiberglass is 1/4" long.

EXAMPLE 25

The procedure of Example 22 is substantially repeated except that thefiberglass is 1/4" long.

                                      TABLE I                                     __________________________________________________________________________                                 Flexural Properties                                                                       Tensile Properties                   Example                                                                            Notched Izod (1/8")                                                                    Gardner Impact                                                                        DTUL   modulus                                                                             strength                                                                            yield failure                        No.  ft. lb./in.                                                                            in. lbs.                                                                              °C. at 264 psi.                                                               (psi × 10.sup.5)                                                              (psi × 10.sup.3)                                                              (psi × 10.sup.3)                                                              (psi × 10.sup.3)         __________________________________________________________________________    1    0.4       12     57     1.85  6.17  5.02  1.86                           2    0.5      <8      66     2.17  6.53  --    --                             3    2.4      <8      102    2.57  8.40  --    --                             4    0.7       30     51     1.78  5.16  --    --                             5    1.5      170     46     1.50  4.24  --    --                             6    8.8      >320    51     1.21  3.29  --    --                             7    0.6       23     45     --    --    --    --                             8    0.7       58     51     --    --    --    --                             9    0.8       58     46     --    --    --    --                             10   0.4       12     62     2.08  6.13  3.95  3.65                           11   0.5      <8      64     2.50  6.44  3.90  3.73                           12   0.4      < 8     70     3.25  6.17  3.70  3.51                           13   0.4      <8      66     3.88  5.73  --    --                             14   0.5       12     54     2.11  5.92  3.92  3.70                           15   0.5       12     55     2.48  6.04  --    --                             16   0.5       12     60     2.95  5.98  3.63  3.48                           17   0.4      <8      57     3.26  5.81  --    --                             18   0.5      <8      61     2.56  6.14  3.83  3.62                           19   0.5      <8      77     4.47  6.06  3.57  3.47                           20   0.4      <8      83     7.06  5.4   --    --                             21   1.0      <8      121    3.39  7.54  --    5.61                           22   1.4      <8      130    5.20  9.42  --    7.10                           23   1.6      <8      133    7.59  11.4  --    --                             24   1.0      <8      99     3.27  6.72  4.82  4.59                           25   1.1      <8      106    5.29  7.65  5.39  5.29                           __________________________________________________________________________

EXAMPLE 26

A five layer sheet, using ethylene vinyl acetate CXA E-136) as the tielayer was prepared by coextrusion. The sheet had the followingstructure:

polycarbonate/ethylene vinyl acetate/ethylene vinyl alcohol/ethylenevinyl acetate/polypropylene.

The thickness of the various layers, in mils, was as follows:

1.3/1.3/3.1/1.6/8.5.

The processing conditions used were as follows:

    ______________________________________                                        Extruder temperatures (°F.)                                                           ethylene vinyl                                                                            polypropyl-                                                                              tie                                     polycarbonate  alcohol     ene        layer                                   ______________________________________                                        Zone 1 500         400         510      360                                   Zone 2 520         410         530      380                                   Zone 3 530         420         540      410                                   Zone 4 540         430         540      --                                    Adapter                                                                              550         430         540      410                                   temp.                                                                         ______________________________________                                    

The die temperature was 500° F. and the feed block temperature was 450°F.

The adhesion of the layers in the sheet was good.

What is claimed is:
 1. A multilayer structure comprising:(i) at leastone polycarbonate layer; (ii) at least one olefin vinyl alcohol layer;and (iii) at least one unmodified polyolefin layer;said layers beingadhered together by means of tie layers disposed therebetween said tielayers being comprised of an olefin vinyl ester copolymer.
 2. Thestructure of claim 1 wherein said unmodified polyolefin ispolypropylene.
 3. The structure of claim 1 wherein said olefin vinylalcohol is ethylene vinyl alcohol.
 4. The structure of claim 3 whereinsaid unmodified polyolefin is polypropylene.
 5. The structure of claim 1wherein said polycrbonate contains at least one recurring structuralunit represented by the formula ##STR4## wherein R is independentlyselected from monovalent hydrocarbon radicals and halogen radicals,A isselected from divalent hydrocarbon radicals, --O--, --S--, --S--S--,##STR5## b is either zero or one, and n is independently selected fromintegers having a value of from 0 to 4 inclusive.
 6. The structure ofclaim 5 wherein b is one.
 7. The structure of claim 6 wherein A is adivalent hydrocarbon radical.
 8. The structure of claim 7 wherein saiddivalent hydrocarbon radicals is 2,2-propylidene.
 9. The structure ofclaim 8 wherein n is zero.
 10. The structure of claim 1 wherein saidolefin vinyl ester copolymer is an olefin vinyl acetate copolymer. 11.The structure of claim 10 wherein said olefin vinyl acetate copolymer isethylene vinyl acetate copolymer.
 12. The structure of claim 11 whereinsaid olefin vinyl alcohol is ethylene vinyl alcohol.
 13. the structureof claim 12 wherein said unmodified polyolefin is polypropylene.
 14. Thestructure of claim 1 which contains one polycarbonate layer, oneunmodified polyolefin layer, and one olefin vinyl alcohol layer adheredtogether by means of said olefin vinyl ester copolymer tie layers. 15.The structure of claim 14 wherein said olefin vinyl alcohol layer is anintermediate layer disposed between a polycarbonate outer layer and anunmodified polyolefin outer layer and is adhered to said outer layers bymeans of said olefin vinyl ester copolymer tie layers.
 16. A multilayerstructure comprising:(i) at least one polycarbonate layer; (ii) at leastone olefin vinyl alcohol layer; and (iii) at least one unmodifiedpolyolefin layer;said layers being adhered together by means of tieslayers disposed therebetween, said tie layers consisting essentially ofa modified polyolefin copolymer.
 17. The structure of claim 16 whereinsaid unmodified polyolefin is polypropylene.
 18. The structure of claim16 wherein said modified polyolefin copolmer is a graft copolymer of apolyolefin and a carboxylic acid or a carboxylic anhydride.
 19. Thestructure of claim 18 wherein said polyolefin portion of said modifiedpolyolefin copolymer is a polymer derived from at least thealpha-olefin.
 20. The structure of claim 19 wherein said alpha-olefim isselected from ethylene, propylene, or mixtures thereof.
 21. Thestructure of claim 18 wherein said carboxylic acid is selected fromacrylic acids and methacrylic acids.
 22. The structure of claim 21wherein said carboxylic acid is acrylic acid.
 23. The structure of claim18 wherein said carboxylic anhydride is maleic anhydride.
 24. Thestructure of claim 16 wherein said olefin vinyl alcohol is ethylenevinyl alcohol.
 25. The structure of claim 24 wherein said unmodifiedpolyolefin is polypropylene.
 26. The structure of claim 16 wherein saidpolycarbonate contains at least one recurring structural unitrepresented by the formula ##STR6## wherein R is independently selectedfrom monovalent hydrocarbon radicals and halogen radicals,A is selectedfrom divalent hydrocarbon radicals, --O--, --S--, ##STR7## b is eitherzero or one, and n is independently seIected from integers having avalue of from 0 to 4 inclusive.
 27. The structure of claim 26 wherein bis one.
 28. The structure of claim 27 wherein A is a divalenthydrocarbon radical.
 29. The structure of claim 28 wherein said divalenthydrocarbon radical is 2,2-propylidene.
 30. The structure of claim 29wherein n is zero.
 31. The structure of claim 16 which contains onepolycarbonate layer, one unmodified polyolefin layer, and one olefinvinyl alcohol layer adhered together by means of said modifiedpolyolefin copolymer tie layers.
 32. The structure of claim 31 whereinsaid olefin vinyl alcohol layer is an intermediate layer disposedbetween a polycarbonate outer layer and an unmodified polyolefin outerlayer and is adhered to said outer layers by means of said modifiedpolyolefin copolymer tie layers.
 33. A multilayer laminar structureconsisting essentially of:(i) at least one polycarbonate layer; (ii) atleast one olefin vinyl alcohol layer; and (iii) at least one unmodifiedpolyolefiin layer; said layers being adhered together by means of tielayers disposed therebetween.
 34. The structure of claim 33 wherein saidunmodified polyolefin is polypropylene.
 35. The structure of claim 33wherein said olefin vinyl alcohol is ethylene vinyl alcohol.
 36. thestructure of claim 35 wherein said unmodified polyolefin ispolypropylene.